In a lamp, such as, for example, a headlamp of a vehicle, a front cover of a lamp housing accommodating a lamp unit is made of a light transmitting resin, and light emitted from the lamp unit is transmitted through the front cover to illuminate the front area of the vehicle in a required light distribution. In the front cover, an effective portion, that is, a region through which the light is transmitted, is molded of a light transmitting resin only. However, an ineffective portion which does not contribute to the light distribution is molded of a colored non-light transmitting resin so that the inside of the lamp housing is optically shielded. Thus, a part of the inside of the lamp is not visible from the outside to improve the beauty of the external appearance. In many cases, such a front cover is molded by a two-color molding method using a light transmitting resin and a non-light transmitting resin as disclosed in Japanese Patent Laid-Open Publication No. 2011-187299.
In the two-color molding method, a cavity is formed using a common die and a primary die, and a first resin is injected into the cavity to mold a first resin portion. Subsequently, the primary die is replaced with a secondary die while the first resin portion is held in the common die, and a second resin is injected into a cavity newly formed using the common die and the secondary die to mold a second resin portion so that a two-color molded article, in which the first resin portion and the second resin portion are integrated with each other is fabricated.